Compared with the cathode ray tube (CRT) display, a liquid crystal display (LCD) has many advantages such as small thickness, low power consumption and the like. Therefore, the CRT displays have been replaced by the LCDs in many fields.
A conventional thin film transistor display panel (TFT-LCD) comprises an array substrate (Array), a color filter substrate (CF) and a liquid crystal layer filled between the Array substrate and the CF substrate. Black matrixes (BMs), a color filter layer (B. G and R color filter), a planarization layer (OC) and spacers (PSs) are sequentially formed on the CF substrate, and manufacturing processes for each layer include a coating process, an exposure process and a development process.
Since a common exposure method is a proximity exposure method, it is required to measure a distance between the mask plate and the glass substrate. FIG. 1 is a structural diagram of a system for measuring the distance between the mask plate and the glass substrate in the prior art, as shown in FIG. 1, the system comprises a semiconductor laser 61, a polarizer 62, a mirror 63, a mask plate 64, a glass substrate 65 and a linear sensor 66. A laser emitted from the semiconductor laser 61 passes through the polarizer 62 so that its light path is adjusted, and then the emitted light beam irradiates onto the mirror 63, the light beam reflected by the mirror 63 passes through the distance measuring window 641 of the mask plate 64 to be incident on the A1 point on the upper surface of the glass substrate 65, the linear sensor 66 receives intensity information of a light beam refracted from the A point on the lower surface of the distance measuring window 641 of the mask plate 64 and of the light reflected from the A1 point on the upper surface of the glass substrate 65, and the intensity information is converted into voltage signals by a AD converter circuit, so that the intensity information of lights at points A1 and A may be expressed. The distance between the mask plate 64 and the glass substrate 65, that is, the distance between the point A1 and the point A, may be measured by analyzing the received voltage signals and obtaining the difference between timings at which these voltage signals are received.
In order to ensure the accuracy of the measured distance data between the mask plate 64 and the glass substrate 65 prior to every exposure, it is required that no other layer exists at the distance measuring window 641 except the black matrix, therefore, the distance measuring window 641 and a peripheral area thereof need to be shielded by using a light shielding plate before layers coated after the black matrix are exposed, so as to prevent the photoresist for the subsequent layers from being cured due to the exposure. In addition, if there is a layer in the shielded peripheral area of the distance measuring window 641, then incomplete exposure at a border area between the shielded region and the unshielded region due to the shielding may easily occur during the exposure, so that debris contamination may be produced in the subsequent development process. Therefore, large blank regions 7 may exist at regions on the motherboard of color filter substrates near the distance measuring windows 641, as shown in FIG. 2.
As shown in FIG. 3, since there are blank regions 7 near the distance measuring windows 641 on the motherboard of the color filter substrates, on the motherboard of the color filter substrates, a segment difference may be caused between the blank region 7 and other nonblank regions, which may cause stress to be concentrated on the aligned and assembled substrates to generate Newton's ring during subsequently aligning and assembling the motherboard of the color filter substrates and the motherboard of the array substrates under vacuum condition, causing the aligned and assembled substrates to distort and the cell thickness is abnormal, thus non-uniformity in the image display may occur when lighting, and local yellowness may occur in a same grey scale.